Absence of lymphatic vessels in term placenta

Abstract

Background: There has been debate about the existence of lymphatic vessels in placenta. Lymphatic endothelial cell (LEC) markers such as LYVE-1 and podoplanin/D2-40 have been found, although PROX1 has not been detected. The most reliable marker for LECs is the double staining for CD31 and PROX1, which has not been performed yet. Methods: We studied three term placentas and dissected them into three areas: i.) basal plate area, ii.) intermediate area, and iii.) chorionic plate area. We used immunofluorescence single and double staining with antibodies against CD31, PROX1, LYVE-1, VEGFR-3, D2-40/PDPN, CD34, CCBE-1, and vimentin, as well as nested PCR, qPCR, Western blot and transmission electron microscopy (TEM). Results: At TEM level we observed structures that have previously mistakenly been interpreted as lymphatics, however, we did not find any CD31/PROX1 double-positive cells in placenta. Absence of PROX1 was also noted by nested PCR, qPCR and Western blot. Also, LEC marker VEGFR-3 was expressed only in a small number of scattered leukocytes but was absent from vessels. The LEC marker D2-40/PDPN was expressed in most stromal cells, and the LEC marker LYVE-1 was found in a considerable number of stromal cells, but not in endothelial cells, which were positive for CD31, CD34, CCBE-1 and vimentin. Additionally, vimentin was found in stromal cells. Conclusions: Our studies clearly show absence of lymphatics in term placenta. We also show that the functional area of the mother's endometrium is not penetrated by lymphatics in term pregnancy.

Analysis of Placental Arteriovenous Formation Reveals New Insights Into Embryos With Congenital Heart Defects

“…This prompted us to question whether there may be a lymphatic network within the chorio-allantoic placenta. To date, lymphatic markers have only been investigated on the maternal side of the placenta ( Pawlak et al, 2019 ) and found to be absent in the term human placenta ( Becker et al, 2020 ). We first screened common lymphatic proteins (PDPN, LYVE1, and PROX1) for expression in the mid-late gestation placenta.…”

Umbilical cord vessels other than the umbilical arteries and vein: a histological study of midterm human fetuses

“…However, venous drainage of the umbilicus was mostly via the abdominal cutaneous veins. Although the pla-centa contains no lymphatic tissues [8], it is likely that thick lymphatic vessels along the umbilical artery drained the umbilical cord at and near the umbilicus. These thick lymphatic vessels are presented in classical textbooks of anatomy, as described by Monie [9].…”

Congenital Infantile Fibrosarcoma Involving Pelvic Wall and Thigh Soft Tissues and Placenta, Presenting with Coagulopathy

“…The morphology and immunophenotype were incompatible with KHE or KLA: positive for vimentin, CD99, and WT1, and negative for CD31, CD34, ERG, D2-40, CD117, HMB45, S100, SMA, calponin, and cytokeratin (AE1/ AE3). The absence of lymphatics in the placenta 7 further ruled against KLA. Infantile fibrosarcoma in the placenta had not been previously reported and was not yet in the differential diagnosis.…”